Determining the concentration of methanol within a liquid mixture of ethanol and methanol using a laser interferometer

This paper investigates using an optical measurement method to determine the concentration ratio in a liquid mixture of methanol and ethanol. To better understand the relative mixture solution concentration, the dilution method is used to determine slight variations in the refractive index of the variable mixture concentration. The test concentration range of both methanol and ethanol is between 0-90%. The results of our analysis indicate that the refractive index of a mixture of methanol and ethanol lies in the interval between the refractive index of pure ethanol and methanol. The optical property of the mixture is similar to that of the solution material with the highest quantity. Regression analysis using a quadratic function resulted in an error of 25%. Regression analysis using a cubic function reduced the error to 6.25%. Therefore, the regression analysis function used in this study is the cubic function, as the mixture solution includes the methanol liquid. Combining the optical measurement and dilution methods can yield the solution concentration of the liquid mixture.